Nanoscale imaging of InN segregation and polymorphism in single vertically aligned InGaN/GaN multi quantum well...

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Vertically aligned Gallium Nitride (GaN) nanorod arrays are crucial for optoelectronic devices.
• Nonpolar Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) multi-quantum wells (MQW) exhibit unique properties but face characterization challenges.
• Understanding nanoscale variations is key to optimizing device performance.

Purpose of the Study:

• To optically investigate the chemical and structural properties of single GaN nanorods with sub-diffraction limit resolution.
• To map variations in chemical composition, charge distribution, and strain within the MQW region.
• To demonstrate the capability of tip-enhanced Raman spectroscopy (TERS) for nanoscale semiconductor analysis.

Main Methods:

• Growth of vertically aligned GaN nanorod arrays with nonpolar InGaN/GaN MQW using Metalorganic Vapor Phase Epitaxy (MOVPE).
• Tip-Enhanced Raman Spectroscopy (TERS) for high-resolution optical investigation of single nanorods.
• High-Resolution Transmission Electron Microscopy (HRTEM) for direct structural confirmation.

Main Results:

• TERS enabled mapping of nanoscale fluctuations in In content (<35 nm resolution) within InGaN layers.
• Evidence of indium clustering and cubic inclusions in the wurtzite matrix near MQW layers was observed.
• HRTEM confirmed the presence of stacking faults and polymorphs near the MQW region.

Conclusions:

• TERS is a powerful, nondestructive tool for nanoscale characterization of semiconductor nanostructures.
• The study highlights TERS's ability to identify and visualize critical nanoscale variations.
• This technique is vital for the optimization of advanced GaN-based nanodevices.